GRB Hubble diagram and constraints on a Λ(t) CDM model

Abstract

In previous papers, a cosmological model with constant-rate particle creation and vacuum term decaying linearly with the Hubble parameter was shown to lead to a good concordance when tested against precise observations: the position of the first peak in the spectrum of anisotropies of the cosmic microwave background (CMB), the Hubble diagram for supernovas of type Ia (SNe Ia), the distribution of large-scale structures (LSS) and the distance to the baryonic acoustic oscillations (BAO). That model has the same number of parameters as the spatially flat standard model and seems to alleviate some observational/theoretical tensions appearing in the later. In this letter we complement those tests with 109 gamma ray bursters (GRB), 59 of them with redshifts above z = 1.4, which permits to extend the Hubble diagram to redshifts up to z ≈ 8. For the calibration of the 50 GRBs with z < 1.4 we use the 288 supernovas of the Sloan Digital Sky Survey (SDSS) project, calibrated with the MLCS2k2 fitter, less model-dependent than other samples like Union2. Our results show a good concordance with the previous tests and, again, less tensions between SNe Ia and GRB best fits as compared to the standard model.

Non-adiabatic Chaplygin gas

“…This set currently constitutes the most precise and reliable observations we have. This concordance has also been confirmed by other complementary tests [34]. This model has no ΛCDM limit.…”

Large-scale structure and integrated Sachs–Wolfe effect in decaying vacuum cosmology

“…Note that, as in the flat ΛCDM model, there are here also only two free parameters. The concordance of this Λ(t) cosmology with Ωm0 ≈ 0.45 has been verified via many different observational data at both the background (Carneiro et al 2006(Carneiro et al , 2008Pigozzo et al 2011;Velten et al 2005) and perturbative (Alcaniz et al 2012;Zimdahl et al 2011;Devi et al 2015) levels.…”

“…The concordance of this Λ(t) cosmology with Ωm0 ≈ 0.45 has been verified via many different observational data at both the background (Carneiro et al 2006Pigozzo et al 2011;Velten et al 2005) and perturbative (Alcaniz et al 2012;Zimdahl et al 2011;Devi et al 2015) levels. Concerning structure formation, the full CMB spectrum has not yet been obtained for this model, but CMB physics can also be accessed via ISW studies, i.e., how time-varying gravitational potential wells change the temperature of the CMB photons as they cross structures (Sachs et al 1967).…”

Model-independent distance calibration of high-redshift gamma-ray bursts and constrain on the ΛCDM model

“…Therefore, they are often proposed as complementary tools to SNe Ia in tracing the Hubble diagram of the high-redshift Universe. Actually, GRBs have already been widely used, either alone or in combination with other data such as SNe Ia, to constrain the cosmological parameters (Schaefer 2003;Bloom, Frail & Kulkarni 2003;Xu, Dai & Liang 2005;Firmani et al 2005;Liang & Zhang 2005;Firmani et al 2006;Schaefer 2007;Wei & Zhang 2009;Wei 2010;Demianski & Piedipalumbo 2011;Wang, Qi & Dai 2011;Capozziello et al 2012;Amati & Della Valle 2013;Wei, Wu & Melia 2013;Velten, Montiel & Carneiro 2013;Cai et al 2013;Bretón & Montiel 2013;Chang et al 2014;Cano & Jakobsson 2014;Cuzinatto, Medeiros & de Morais 2014;Wang, Dai & Liang 2015;Li, Ding & Zhu 2015). Unfortunately, since the explosion mechanism of GRBs is still not clearly known, the distance calibration of GRBs is not as easy as that of SNe Ia.…”